Moved all the content of the DDK files ntdef.h and ntddk.h to
winternl.h.

diff --git a/scheduler/syslevel.c b/scheduler/syslevel.c
index 974650d..68dcb86 100644
--- a/scheduler/syslevel.c
+++ b/scheduler/syslevel.c
@@ -24,7 +24,7 @@
 # include <unistd.h>
 #endif
 #include <sys/types.h>
-#include "ntddk.h"
+#include "winternl.h"
 #include "syslevel.h"
 #include "stackframe.h"
 #include "wine/library.h"